Benchmark AHB2 Power Amplifier

by: Benchmark Media Systems, Inc.



 

 

Trade in your old Audio Power Amplifier and Save up to $750 on a Benchmark AHB2!*

* Online (from benchmarkmedia.com) or phone orders (1-800-262-4675) only. USA and Canadian sales only.


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    True High-Resolution Performance 

    The AHB2 is the ideal match to the performance limits of High-Resolution-Audio (HRA) formats. Benchmark's AHB2 power amplifier delivers musical details without introducing the masking effects of amplifier noise and distortion. The dynamic range of the AHB2 is 132 dB, making it 10 to 30 dB quieter than some of the very best reference-quality power amplifiers.

    The frequency response of the AHB2 extends beyond 200 kHz. With the AHB2, you will discover previously overlooked nuances, dynamics, and detail in your favorite recordings and experience the full potential of the latest high-resolution 24-bit PCM and 1-bit DSD audio formats.

    Experience the Emotion

    The musical details and emotion captured on today's finest High-Resolution-Audio recordings can only be fully appreciated when every component in the signal chain is capable of true high-resolution performance. Power amplifiers are a weak link in most audio systems. Most power amplifiers are well matched to the limitations of the CD format, but they fall well short of the capabilities of high-resolution formats. In contrast, the revolutionary AHB2 was specifically designed to deliver true high-resolution performance.

    THE NEED FOR BETTER AMPLIFICATION

    D/A conversion technology has outpaced the development of new power amplifiers. This means that the power amplifier has become a limiting factor in many audio systems. For example, the noise and distortion produced by the Benchmark DAC2 D/A converter is 20 to 30 dB lower than that produced by most high-quality power amplifiers. Until now, this meant that the DAC2 could not be fully appreciated. Benchmark set out to solve this problem by creating an amplifier that matches the performance of the DAC2.

    INTRODUCING THE AHB2 - A NEW AND DIFFERENT POWER AMPLIFIER

    We had to look beyond existing amplifier technologies and explore some new and radical solutions. In our search, we learned of two new patents on a new amplifier technology from THX. This was exactly the technology we needed to build our new amplifier.

    The AHB2 uses the new and revolutionary THX-patented AAA(TM) technology to virtually eliminate all forms of distortion. This technology uses feed-forward error correction to eliminate the distortion that is normally produced by the output stage.  No other audio amplifier comes close to delivering the clean, quiet, and robust power of the AHB2.

    In our quest, we also focused on frequency response, output noise, drive current, damping factor, and reliability. The result is an amplifier that stands head and shoulders above the competition.

    The Quietest, Cleanest Audio Amplifier on the Planet

    From the first watt to the last watt, no audio power amplifier offers lower noise or lower distortion than the Benchmark AHB2. Benchmark has raised the bar by introducing a new and revolutionary amplifier!

    “I measured less distortion and noise in the AHB2 than in any other of the many power amps I've measured over the years.”

    -Bascom King, BHK Labs

    “If ever there were a giant-killer of an amp, this is it.”

    "It is one of the -- if not the -- quietest, most resolving amps I've heard. Time and again, without ever having intended to, I wound up hours deep in listening to the fringes of my music collection, thanks to the AHB2’s reference-level transparency and obscene athleticism."

    - Hans Wetzel, SoundStage!

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    The AHB2 has been internationally recognized for its groundbreaking technology, performance, and transparent sound.

    [powr-photo-gallery id=38247f01_1458569008900]

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    Sonic Purity that Surpasses Class A!

    The AHB2 is a linear amplifier that surpasses the sonic purity of all class-A amplifiers. No amplifier delivers lower noise or lower distortion. The small, passively cooled chassis, cleanly delivers 480 Watts bridged mono into 6 Ohms, with additional reserves for driving difficult speaker loads. Unlike power-hungry class-A amplifiers, the AHB2 achieves a power efficiency that rivals that of a Class D (switching) power amplifier.

    Difficult Speaker Loads are Handled With Ease

    Many loudspeakers have frequencies at which their impedance drops to levels that are much lower than the "nominal" impedance. The AHB2 drives difficult phase angles and low impedances with ease. Stereo loads as low as 1.4 Ohms can be cleanly driven to full output levels. Most power amplifiers produce higher levels of distortion when the load impedance decreases. In contrast, the feed-forward error correction system in the AHB2 keeps the output clean when driving difficult loads. The AHB2 produces almost no measurable distortion at any rated load condition.

    High Damping Factor

    The AHB2 has a high damping factor that augments its extended low-end to deliver solid, well-controlled bass. This high damping factor also keeps the frequency response absolutely flat while driving speakers with large frequency-dependent impedance variations.

    High Output Current

    The AHB2 can deliver up to 29 A peak to each channel simultaneously. This robust drive current easily handles some of the most demanding loudspeakers. The AHB2 has tightly regulated power supplies that keep the output clean while delivering high current.

    Distortion is Below Audibility

    The AHB2 will never produce audible distortion. In most playback systems, the distortion produced by the AHB2 will never even reach the 0 dB SPL threshold of hearing. This means that the distortion could not be heard, even if it could be played while the music was muted.

    The AHB2 allows you to escape the distortion limitations of classic amplifier topologies and enter the world of high-resolution audio playback.

    "I very much enjoyed my time evaluating the Benchmark AHB2 amplifier and can heartily recommend it to those seeking one of the lowest distortion and lowest noise amplifiers on the planet—one that is very musically transparent and easy on the ears to boot."

    - Frank Alles, Stereo Times

    Extreme Performance Often Requires a Radical Approach

    The AHB2 amplifier is radically different than traditional audio amplifiers. Two new THX-patented feed-forward error-correction technologies eliminate most sources of distortion. An unconventional power supply maintains tight regulation and low ripple while minimizing magnetic fields. A low-gain topology optimizes the gain staging between the D/A converter and the power amplifier while minimizing noise. Sophisticated shielding and star-quad signal distribution provide outstanding immunity to interference. A unique output stage incorporates class-H tracking power supply rails to improve efficiency. The result is that the cool-running AHB2 has a signal to noise ratio of 132 dB while distortion is at or below the measurement limits of the finest test equipment.

    See John Siau's application note: "A Radical Approach to Power Amplification" for more details.

    Introducing THX Achromatic Audio Amplifier Technology™

    The AHB2 is the only amplifier that leverages the patented THX-AAA Technology™. This patented system reduces distortion to vanishingly low levels while enabling several power-saving techniques.

    "The Benchmark AHB2 is a powerful and efficient amplifier with prodigious low levels of noise and distortion. The fact that it is also very musical and non-fatiguing, courtesy of THX’s patented AAA Technology™, is the icing on the cake. Benchmark Media and THX have a lot to be proud of for the development and implementation of the new technology the AHB2 represents."

    - Frank Alles, Stereo Times

    Bipolar Class-AB Output Stage

    The AHB2 has a bipolar class-AB output stage that delivers high output current and low noise. The THX-AAA Technology™ provides accurate cancellation of zero-crossing errors, exceeding the performance of the best class-A amplifier.

    Feed-Forward Error Correction

    Traditional class-AB amplifiers generate crossover distortion every time the push-pull output stage crosses 0 volts. This crossover distortion can be especially problematic at low playback levels.

    In contrast, class-A amplifiers eliminate crossover distortion by keeping all output devices turned on at all times. This brute-force class-A approach solves the crossover distortion problem but it consumes lots of power while delivering very little to the speakers. The wasted power produces heat which must be dissipated into the listening space.

    Class-A amplifiers eliminate crossover distortion but they suffer from high power consumption, poor damping, and limited output power. The AHB2 is the first amplifier to virtually eliminate crossover distortion without incurring the undesirable side effects of class-A amplification.

    The Importance of the First Watt

    Dick Olsher once said that "the first Watt is the most important Watt". We agree! From the first Watt to the last Watt, the AHB2 shows no evidence of crossover distortion.

    In contrast, all conventional class-AB amplifiers have crossover-distortion artifacts.Traditional class-AB designs attempt to control distortion through the use of feedback. Unfortunately, these feedback systems have a limited ability to reduce the abrupt transients that are caused by output device crossover transitions. Feedback networks attempt to correct errors after they occur. In contrast, feed-forward networks can prevent errors before they occur.

    THX-AAA Technology™ includes an ultra-clean low-power error-correction amplifier that runs in parallel with the high-power main amplifier. The correction amplifier actively drives the output while the main output devices transition between push and pull states. Like a class-A amplifier, the AHB2 shows no signs of crossover distortion. The feed-forward system virtually eliminates the errors that would have been produced by the output devices in the main amplifier.

    High Efficiency - Green Never Sounded so Good!

    The THX-patented feed-forward error correction used in the AHB2 is so effective that biasing of the class-AB bipolar output devices can be reduced to unusually low levels. Benchmark has chosen to maintain a small bias current in the output stage, but this bias current is not critical to the distortion performance of the unit. The benefit of low bias current is that very little power is wasted as heat when the amplifier is idle. The AHB2 only draws 12 W when idle, and less than 1/2 W in standby.

    The feed-forward error correction also allows the use of class-H tracking power supply rails without the usual distortion-performance penalty.  These tracking rails significantly improve the overall efficiency of the amplifier while the error correction keeps distortion nearly nonexistent. The AHB2 rivals the efficiency of class-D amplifiers while exceeding the sonic performance of power-hungry class-A designs. Green never sounded so good!

    Innovative Low-Noise Power Supply

    Most high-quality power amplifiers have linear power supplies, large toroidal transformers, and large banks of energy-storage capacitors. These linear supplies are usually unregulated and the capacitors help to remove ripple produced by the audio and by the AC line. In contrast, the AHB2 uses a tightly regulated resonant switching power supply that includes a very fast control loop. This control loop responds to audio-frequency load changes and keeps the supply voltage constant without the use of a large bank of capacitors. This active regulation is much more effective than capacitive energy-storage. Consequently, the peak power output of the AHB2 does not vary with line voltage or audio loading. The power supply rails maintain a constant voltage during audio peaks.

    The power supply in the AHB2 switches at frequencies that are well above audible frequencies. This eliminates mechanical hum while significantly reducing the strength of stray magnetic fields. For a given amount of power, magnetic field strength decreases as switching frequency increases. The lower field strengths also provide a significant reduction in size. High-frequency transformers and coils are also much smaller than line-frequency components. This size reduction contributes to the small physical size of the AHB2.

    The switching power supply used in the AHB2 is a zero-voltage switching, resonant power converter. This means that the power devices in the supply switch near zero voltage and zero current, eliminating the large switching transients produced by conventional switching power supplies. The power supply in the AHB2 is actually much cleaner and quieter than a conventional linear supply. 

    The power supply In the AHB2 is well over 90% efficient, much more efficient than linear supplies. This means that little power is lost to heat.

    Passive Cooling

    The power-efficient AHB2 uses passive heat sinks to maintain cool operation. The AHB2 delivers high power without the need for fans. The unit runs cool, even when playing audio at full output levels. The absence of fan noise is absolutely essential in a high-resolution listening environment.

    Low-Noise Input Amplifiers

    The precision balanced inputs on the AHB2 are equipped with low-noise input amplifiers. Benchmark considers balanced inputs essential in a true high-resolution system. If balanced sources are not available, Benchmark sells unbalanced to balanced adapter cables that extend a 3-wire balanced connection back to the unbalanced source connectors. These adapter cables provide many of the advantages of fully balanced interconnects while providing full compatibility with all unbalanced sources.

    Low Gain for Low System Noise

    The AHB2 is a low-gain design. Maximum output is not reached until the balanced inputs reach +22 dBu. This is a much higher signal level than is used at the input of most power amplifiers. High interface signal levels are required to achieve the best possible system signal to noise ratio (SNR). Most power amplifiers have far too much gain and consequently they suffer from poor noise performance. The AHB2 is 10 dB to 30 dB quieter than some of the very best power amplifiers on the market. A rear-panel gain switch can be used to set the AHB2 at higher gain settings if necessary. The low-gain setting is designed to interface directly with Benchmark DAC2 converters and other professional audio products.

    Bulletproof Protection System - No Relays

    The AHB2 has a unique protection system that prevents damage from overloads and short circuits. The protection system monitors output voltage, output current, output distortion, output device SOA (safe operating area), power supply current, power supply voltage, AC line voltage, case temperatures, and power device temperatures. Fault conditions silently mute both output channels in order to protect the speakers and amplifier from damage. The amplifier outputs are also muted while the amplifier is turning on or off.

    The mute circuits are fully electronic. There are no mechanical relays in the mute circuits. Our tests showed that relays are too slow to protect against certain fault events. Our tests also showed that relay contacts can add significant distortion as they deteriorate with use. The AHB2 is one of very few amplifiers that avoids the use of relays in the output stage. This means that the AHB2 will maintain its rated distortion performance after an unlimited number of power on/off cycles. 

    Benchmark's unique distortion monitoring system mutes the amplifier if it is excessively driven into clipping. This system protects tweeters from an overdriven amplifier.

    Benchmark's short circuit detection system is fast enough to fully protect the amplifier from events occurring at any output voltage or current. This system detects abnormal loads and instantly mutes the outputs. 

    A status display shows the exact cause of the fault so that the problem can be corrected.

    SpeakON Output Connectors

    The AHB2 is equipped with high-quality binding posts, and SpeakON output connectors. The high-current SpeakON connectors are designed for heavy-duty commercial sound systems and provide much better electrical connections than binding posts. Benchmark highly recommends the use of the twist-lock SpeakON output connectors. We also highly recommend the use of our top-quality professional-grade speaker cables.

    A.H.B.

    The letters A, H, and B allude to the unique topology of the amplifier's output stage. The AHB2 combines class-AB, and class-H topologies using a feed-forward error correction system.

    But there is much more to the story -

    The initials A.H.B. can be found on many of the circuit diagrams of Benchmark's early products dating back as far as 1983. These are the initials of Benchmark's founder, Allen H. Burdick. He personally designed many of Benchmark's early products.

    Allen had a life-long passion for audio, and he became one of the leading innovators in the pro-audio industry. The AHB2 is named in his memory.

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    Output Power

    1 kHz, < 0.0003 % THD+N

    • 100 Watts per channel into 8 Ohms, both channels driven
    • 130 Watts per channel into 6 Ohms, both channels driven
    • 190 Watts per channel into 4 Ohms, both channels driven
    • 240 Watts per channel into 3 Ohms, both channels driven
    • 200 Watts Bridged Mono into 16 Ohms
    • 380 Watts Bridged Mono into 8 Ohms
    • 480 Watts Bridged Mono into 6 Ohms

    All speakers have variations in input impedance. Select loads based on nominal impedances not minimum impedances.

     SNR & Dynamic Range

    Rated output relative to output noise, inputs shorted

    • 132 dB A-weighted, Stereo Mode
    • 135 dB A-weighted, Mono Mode
    • 130 dB Unweighted, 20 Hz to 20 kHz, Stereo Mode
    • 133 dB Unweighted, 20 Hz to 20 kHz, Mono Mode

    Noise Voltage

    Output noise voltage, inputs shorted

    • 7.1 uV, A-weighted, Stereo Mode
    • 9.8 uV, A-weighted, Mono Mode

    Noise Power Relative to 1 Watt

    Output noise power, inputs shorted

    • -115 dB Watts, A-weighted, 16-Ohm Load, Stereo Mode
    • -112 dB Watts, A-weighted, 16-Ohm Load, Mono Mode
    • -112 dB Watts, A-weighted, 8-Ohm Load, Stereo Mode
    • -109 dB Watts, A-weighted, 8-Ohm Load, Mono Mode
    • -111 dB Watts, A-weighted, 6-Ohm Load, Stereo Mode
    • -108 dB Watts, A-weighted, 6-Ohm Load, Mono Mode
    • -109 dB Watts, A-weighted, 4-Ohm Load, Stereo Mode

    THD+N

    1 kHz, 80 kHz LPF, at full rated output into any rated load

    • < -118 dB (< 0.00013%), Stereo Mode
    • < -118 dB (< 0.00013%), Mono Mode

    THD

    1 kHz, 20 kHz LPF, at full rated output into any rated load

    • -119 dB (< 0.00011%), Stereo Mode
      • < -120 dB (< 0.00010%), Mono Mode

      Crosstalk

      • Better than -115 dB at 1 kHz
      • Better than -92 dB at 20 kHz

      Frequency Response

      • Better than 0.1 Hz to 200 kHz, +0/-3 dB
      • -0.01 dB at 20 Hz, -0.17 dB at 20 kHz, 8-Ohm Load
      • -0.23 dB at 20 Hz, -0.32 dB at 20 kHz, 4-Ohm Load

      Damping Factor

      • 350 at 20 Hz, 8-Ohms
      • 254 at 1 kHz, 8-Ohms
      • 34 at 20 kHz, 8-Ohms
      • 7 at 200 kHz, 8-Ohms 

      Maximum Audio Output Current

      • 29 A peak, per channel, both channels driven

      Input Sensitivity

      • Low-Gain = 22 dBu (9.8 Vrms), Gain = 9.2 dB
      • Mid-Gain = 14.2 dBu (4 Vrms), Gain = 17.0 dB
      • High-Gain = 8.2 dBu (2 Vrms), Gain = 23 dB
      • Use Mid-Gain or High-Gain settings for unbalanced inputs
      • Unbalanced inputs require RCA to XLRM adapter cables 

      Input Impedance

      • 50 k Ohms, normal mode
      • 1 M Ohm, common mode

      Input CMRR

      • 80 dB at 20 Hz, typical
      • 80 dB at 1 kHz, typical
      • 65 dB at 20 kHz, typical

      Trigger I/O

      • 12 VDC 200 mA current-limited output to trigger turn-on of remote devices
      • DC input for slaving to remote devices
      • Input responds to 3.3 V logic and higher, VIL = 1.26 V, VIH = 2.7 V
      • Absolute maximum input voltage = 30 VDC
      • Absolute minimum input voltage = -0.3 VDC
      • Input Impedance = 20 k Ohms

      Protection Circuits

      • Fully Electronic, No Relays
      • Mute Sequencing
      • Distortion Detection
      • Short Circuit Detection
      • Over Current Detection
      • Over Temperature Detection
      • SOA Detection (Output device safe operating area)

      Dimensions

      Non-rack-mount version:

      • 11.04" W x 3.88" H x 9.34 " D - Including feet and binding posts
      • 11.04" W x 3.47" H x 8.33 " D - Excluding feet and connectors
      • Faceplate height is 2RU

      Rack-mount version:

      • 19.00" W x 3.88" H x 10.62 " D - Including binding posts, handles and removable feet
      • 19.00" W x 3.47" H x 8.33 " D - Excluding feet and connectors
      • 9.09" rack depth, including binding posts, excluding cables
      • 11" rack depth, including cables
      • Faceplate height is 2RU

      Weight

      • 12.5 lbs., 16 lbs. shipping - Non-rack-mount version
      • 13.5 lbs., 17 lbs. shipping - Rack-mount version

      AC Input

      • Auto-ranging AC Input
      • 100 to 120 VAC +/- 10%, 8 Amps, 50 - 60 Hz
      • 220 to 240 VAC +/- 10%, 8 Amps, 50 - 60 Hz
      • Idle Power Consumption = 20 W
      • Standby Power Consumption < 0.5 W

      Manual

      Detailed specifications and performance plots are available in the downloadable manual.

      Download the AHB2 Manual →

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      AHB2 LAB EVALUATION - AVMENTOR.NET

      Benchmark Media Systems - June 15, 2016

       

      

      AHB2 - "THIS STABLE AND LOAD-INDEPENDENT BEHAVIOR ... IS SOMETHING NOT OFTEN ENCOUNTERED"

      "AHB2's output power ... easily confirmed the specs given by the company itself."

      "Based on this performance, the amplifier seems more than capable of driving difficult loads."

      "Damping factor was estimated above 200, therefore, no system frequency response discrepancies, due to loudspeaker's impedance variability, should be expected."

      "In distortion measurements, AHB2's behavior was impressive ..."

      "The amplifier's spectral behavior does not seem to change significantly with a 4-Ohm load at its outputs."

      "This stable and load-independent behavior of the output stage is something not often encountered."

      "This performance clearly shows that the Benchmark/THX design approach works ... the result is a power stage with very low distortion, indeed."

      "The noise performance of the amplifier was, also, top-class ... there is an apparent absence of noise components from the power supply ... this is a remarkable behavior, especially with the output stage under load conditions ..."

      - Dimitris Stamatakos, AVMENTOR.net

      View full article →

      DAC2 & AHB2 REVIEW - DIMITRIS STAMATAKOS, AVMENTOR.NET

      Benchmark Media Systems - June 02, 2016

       

      AHB2 - "A CONVINCING EXAMPLE OF WHAT THE FUTURE OF POWER AMPLIFIERS CAN BE"

      "Benchmark dared to engage their power amplifier project from a different angle, discarding the standard approach ... and certainly succeeded. The theoretical advantages of their choices are both evident in the laboratory and heard during the listening sessions, thus justifying the whole approach."

      "Based on a very interesting set of ideas, with a long history but few examples of a practical application, the Benchmark AHB2 could serve as a convincing example of what the future of power amplifiers can be. Combine it with a renowned D/A Converter like the DAC2 HGC, and what you have is a top quality system from which only the loudspeakers are missing!"

      DAC2AHB2 - "THE BEST PREAMPLIFIER/POWER AMPLIFIER ... IN THIS PRICE RANGE"

      "Overall, the DAC HGC/AHB2 pair is the best preamplifier/power amplifier we had the opportunity to listen to in recent years in this price range."

      - Dimitris Stamatakos, AVMENTOR.net

      View full article →

      AHB2 REVIEW - PAUL RIGBY, THE AUDIOPHILE MAN

      Benchmark Media Systems - June 01, 2016

       

      AHB2 - "THE PERFECT HEART TO ANY HIFI"

      "Neat in construction, busy in terms of features and small in stature, the AHB2 is quite remarkable in how it goes about its business of delivering music. I’ve seldom heard such a balanced, easy on the ear power amplifier as this that also provides tonal accuracy plus an attractive space in the midrange. The AHB2 would be an ideal fulcrum to any hi-fi system, acting as the heart around which you can build up your hi-fi chain. It’s dependable and rock solid. The perfect heart to any hifi."

      - Paul Rigby, The Audiophile Man - audiophileman.com

      View full article →

      AHB2 REVIEW - PAUL SEYDOR, THE ABSOLUTE SOUND

      Benchmark Media Systems - May 13, 2016

       

      AHB2 - "ESSENTIALLY PERFECT"

      "Benchmark products ... are made for the professional market (where they are ubiquitous) and designed to the most exacting standards of performance and reliability."

      "Within a remarkably short period of time ... my mental processes shifted from comparison mode to enjoying music, all the attention drawn to the source material and the rare sensation of feeling as if I were listening back to the source."

      "... the AHB2 gets as high, enthusiastic, and confident a thumbs up as my arm is capable of reaching."

      - Paul Seydor, The Absolute Sound, April 2016

      View full article →

      AHB2 AWARD - "CLASS A RECOMMENDED COMPONENT", STEREOPHILE

      Benchmark Media Systems - March 22, 2016

       

      AHB2 - RECEIVES STEREOPHILE'S HIGHEST RATING!

      "CLASS A RECOMMENDED COMPONENT, 2016"

      "More apparent low-level detail" - KR

      "In his listening tests, Kalman Rubinson discovered 'much more apparent low-level detail in already-familiar recordings' - a characteristic he credited to the Benchmark's evident noiselessness - and a tonal balance that 'sounded more right' than any of the other amps on hand."

      "An extraordinary amplifier" - JA

      "In measuring the AHB2 and attempting to confirm its specified very high signal/noise ratio, John Atkinson observed nonlinearities in his testing equipment that 'Haven't affected the measured performance of other amplifiers I've tested, but they were detectable with the AHB2's very low intrinsic distortion and noise.' His conclusion: 'an extraordinary amplifier.'"

      The AHB2 shares the elite "Class A Recommended" category with amplifiers costing 10 to 20 times more.

      View full article →

       

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      Click here to view a list of recommended accessories for your AHB2!

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      Manual

      Detailed specifications and performance plots are available in the downloadable manual.

      AHB2 Manual

      AHB2 Application Notes

      AHB2 App Notes

      Reviews

      AHB2 Reviews

     

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    DESIGNED, ASSEMBLED, AND TESTED IN THE USA

    This Benchmark product was designed, assembled, and tested in the USA using USA and imported components. Most major components are made in USA.



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